BOPs often operate in extremely cold environments where temperatures reach below -40.degree.. All of these BOPs operate under high pressure and contain rubber parts which provide a sealing function for the well contents. Extreme cold can affect the sealing function of the rubber parts and this can lead to failure of the seal, resulting in a dangerous environment. In addition, normal cold weather operation of the BOP can lead to a build-up of frost or rime in the bore of the BOP which impairs its safety.
In the past, methods of heating BOPs have involved: heating water in a boiler, and transferring the heat from the heated water to the BOP through a heat exchanger; or blowing air through a heated glycol filled radiator onto the surface of the BOP. These methods were inefficient due to a loss of heat to the environment.
Another method utilized a rigid box or container surrounding the BOP. While this improved heat retention, access to the BOP was restricted.